1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel wherein sustain discharge spaces can be arranged at an equal distance.
2. Description of the Related Art
Generally, a plasma display panel (PDP) is a display device utilizing a visible light emitted from a fluorescent body when an ultraviolet ray generated by a gas discharge excites the fluorescent body. The PDP has an advantage in that it has a thinner thickness and a lighter weight in comparison to the existent cathode ray tube (CRT) and is capable of realizing a high resolution and a large-scale screen. The PDP includes of a plurality of discharge cells arranged in a matrix pattern, each of which makes one pixel of a field.
FIG. 1 is a perspective view showing a discharge cell structure of a conventional three-electrode, alternating current (AC) surface-discharge PDP.
Referring to FIG. 1, a discharge cell 1 of the conventional three-electrode, AC surface-discharge PDP includes a first electrode 12Y and a second electrode 12Z provided on an upper substrate 10, and an address electrode 20X provided on a lower substrate 18. Such a discharge cell 1 is arranged at a panel in a matrix type as shown in FIG. 2.
On the upper substrate 10 provided with the first electrode 12Y and the second electrode 12Z in parallel, an upper dielectric layer 14 and a protective film 16 are disposed. Wall charges generated upon plasma discharge are accumulated into the upper dielectric layer 14. The protective film 16 prevents a damage of the upper dielectric layer 14 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from magnesium oxide (MgO).
A lower dielectric layer 22 and barrier ribs 24 are formed on the lower substrate 18 provided with the address electrode 20X. The surfaces of the lower dielectric layer 22 and the barrier ribs 24 are coated with fluorescent layers 26. The address electrode 20X is formed in a direction crossing the first electrode 12Y and the second electrode 12Z. The barrier rib 24 is formed in parallel to the address electrode 20X to prevent an ultraviolet ray and a visible light generated by a discharge from being leaked to the adjacent discharge cells.
The fluorescent layers 26 is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive gas for a gas discharge is injected into a discharge space defined between the upper and lower substrate 10 and 18 and the barrier rib 24. A black matrix 30 is formed between the first electrode 12Y and the second electrode 12Z which are provided at the adjacent discharge cells 1.
Such an AC surface-discharge PDP drives one frame, which is divided into various sub-fields having a different discharge frequency, so as to express gray levels of a picture. Each sub-field is again divided into an initialization period for uniformly causing a discharge, an address period for selecting the discharge cell and a sustain period for realizing the gray levels depending on the discharge frequency. For instance, when it is intended to display a picture of 256 gray levels, a frame interval equal to {fraction (1/60)} second (i.e. 16.67 msec) is divided into 8 sub-fields. Each of the 8 sub-fields is divided into an address period and a sustain period. Herein, the reset period and the address period of each sub-field are equal every sub-field, whereas the sustain period are increased at a ration of 2n (wherein n=0, 1, 2, 3, 4, 5, 6 and 7) at each sub-field. Since each sub-field has a different sustain period, it is able to express a gray scale of a picture.
In the reset period, a reset pulse is applied to the first electrode 12Y to cause a reset discharge. In the address period, a scanning pulse is applied to the first electrode 12Y and a data pulse is applied to the address electrode 20X, to thereby cause an address discharge between two electrodes 12Y and 20X. Upon address discharge, wall charges are formed at upper and lower dielectric layers 14 and 22. In the sustain period, an alternating current applied alternately to the first electrode 12Y and the second electrode 12Z generates a sustain discharge between the first electrode 12Y and the second electrode 12Z.
However, such an AC surface-discharge PDP has a sustain discharge that concentrates on the center of the upper substrate 10, to thereby deteriorate the utility of a discharge space. Accordingly, it has a problem in that a discharge area is reduced to deteriorate a light-emission efficiency. In order to solve such a problem, a four-electrode PDP as shown in FIG. 3 has been suggested.
FIG. 3 and FIG. 4 show a conventional four-electrode AC surface-discharge PDP.
Referring to FIG. 3 and FIG. 4, a discharge cell 50 of the conventional four-electrode AC surface-discharge PDP includes a first electrode T, a second electrode Y and a third electrode Z provided on an upper substrate 32, and an address electrode A provided on a lower substrate 38. Such a discharge cell 50 is arranged in a matrix type as shown in FIG. 4.
The first electrode T and the second electrode Y have a narrow gap while the third electrode Z has a wide gap from the second electrode Y. On the upper substrate 32 provided with the first to third electrodes T, Y and Z in parallel, an upper dielectric layer 34 and a protective film 36 are disposed. Wall charges generated upon plasma discharge are accumulated into the upper dielectric layer 34. The protective film 36 prevents a damage of the upper dielectric layer 64 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. The protective film 36 is usually made from a magnesium oxide (MgO).
A lower dielectric layer 42 and barrier ribs 44 are formed on the lower substrate 38 provided with the address electrode A. The surfaces of the lower dielectric layer 42 and the barrier ribs 44 are coated with fluorescent layers 46. The address electrode A is formed in a direction crossing the first electrode to third electrodes T, Y and Z. The barrier rib 44 is formed in parallel to the address electrode A to prevent an ultraviolet ray and a visible light generated by a discharge from being leaked to the adjacent discharge cells.
The fluorescent layer 46 is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive gas for a gas discharge is injected into a discharge space defined between the upper and lower substrate 32 and 38 and the barrier rib 44. A black matrix 40 is formed between the third electrode Z and the first electrode T which are provided at the adjacent discharge cells.
In the reset period, a reset pulse is applied to any one of the first to third electrodes T, Y and Z to cause a reset discharge within the discharge cell 50. In the address period, a scanning pulse is applied to the first or second electrode T or Y and a data pulse is applied to the address electrode A, to thereby cause an address discharge between the first or second electrode T or Y and the address electrode A. Upon address discharge, wall charges are formed at upper and lower dielectric layers 34 and 42. In the sustain period, a sustain pulse is alternately applied to the second electrode Y and the third electrode Z to thereby generate a sustain discharge at the two electrodes Y and Z.
In such a conventional four-electrode AC surface-discharge PDP, a utility of the discharge space is improved because the second electrode Y and the third electrode Z causing a sustain discharge is set to have a wide gap from each other. Accordingly, a discharge area is enlarged to enhance a light-emission efficiency.
However, the conventional four-electrode AC surface-discharge PDP is supplied with a sustain pulse having a high voltage level than the three-electrode AC surface-discharge PDP because it causes a sustain discharge between the second electrode Y and the third electrode Z that are set at a wide gap. Accordingly, an erroneous discharge may be generated between the third electrode Z and the first electrode T being adjacent to each other with having the black matrix 40 therebetween. In other words, since different electrodes are provided with being intervened with the black matrix 40 to thereby generate a desired voltage difference, an erroneous discharge may occur between the adjacent discharge cells.
In order to overcome such an erroneous discharge phenomenon, there has been suggested a four-electrode AC surface-discharge PDP as shown in FIG. 5.
FIG. 5 shows a four-electrode PDP according to another conventional embodiment.
Referring to FIG. 5, the PDP according to another conventional embodiment has the same electrodes that are adjacent to each other with having black matrices 58 and 60 therebetween. In other words, first and second discharge cells 52 and 54 being adjacent to each other at the upper and lower portion are adjacent to an identical electrode Z with having the first black matrix 58 therebetween. Further, second and third discharge cells 54 and 56 being adjacent to each other at the upper and lower portion are adjacent to an identical electrode T with having the second black matrix 60 therebetween. In other words, the electrodes T, Y and Z shown in FIG. 5 are arranged in a mirror type around the black matrices 58 and 60.
If the same electrodes Z, Z or T, or T are provided with having the black matrices 58 and 60 therebetween, then an erroneous discharge is not generated between the adjacent discharge cells 52, 54 and 56. In other words, the adjacent electrodes Z, Z or T, or T are supplied with pulses having the same polarity, so that an erroneous discharge between the adjacent discharge cells 52, 54 and 56 can be prevented.
In such a conventional four-electrode AC surface-discharge PDP, the first electrode T and the second electrode Y have a narrow distance D1 from each other while the second electrode Y and the third electrode Z have a wide distance D2 have a wide distance D2. In the four-electrode AC surface-discharge PDP, a discharge space D2 between the second electrode Y and the third electrode Z contributes to a real brightness. The discharge space D2 positioned within each discharge cell 52, 54 and 56 must be arranged at an equal distance. In other words, all the discharge spaces D2 are arranged at an equal distance such that the PDP has a uniform brightness. However, in the four-electrode PDP as shown in FIG. 5, the discharge cells fails to be arranged at an equal distance.
More specifically, the discharge space D2 of the first discharge cell 52 and the discharge space D2 of the second discharge cell 54 are spaced at a first distance D3 from each other. Otherwise, the discharge space D2 of the second discharge cell 54 and the discharge space D2 of the third discharge cell 56 are spaced at a second distance (i.e., D1+D3+D1) larger than the first distance D3 from each other. In other words, the discharge cells 52, 54 and 56 fails to be set at an equal distance.
If the discharge cells fails to be arranged at an equal distance as mentioned above, then a brightness at the first distance D3 is set to be different from a brightness at the second distance D1+D3+D1 as shown in FIG. 6. In other words, since the second distance D1+D3+D1 is set widely, a light generated at the second distance D1+D3+D1 has a lower brightness than a light generated at the first distance D1. As a result, the PDP shown in FIG. 5 fails to display a uniform picture and generates a stripe at its horizontal line.